For authorized user equipment (UE for short) that has signed a network access protocol with an operator, to normally use a subscribed service over a network, each time the UE is powered on, the UE needs to complete, on the network of the operator, a procedure of registering with and attaching to the network; or after a preset time since the UE completely leaves coverage of the network, the UE needs to complete again, on the network of the operator, a procedure of registering with and attaching to the network; or when entering from an area of the network of the operator to another area, the UE needs to perform a routing area update procedure.
Currently, because on-net UEs subscribe to different services and have different charging standards, an operator expects to classify mobility management entities (MME for short), and different MMEs process access requests of UEs that subscribe to different services. In this way, users subscribing to different services are logically managed separately, which can improve management efficiency of a communications operator. For example, for all user equipments that subscribe to an M2M service, a group of dedicated MMEs are used for management; for all user equipments that do not subscribe to an M2M service, another group of MMEs are used for management.
However, in a Long Term Evolution (LTE for short) network, when UE executes an attach procedure or a routing area update procedure, an evolved node eNodeB selects an MME for the UE by depending on only a network topology. In this way, it is possible that the eNodeB selects a wrong MME for the UE. Therefore, in a case in which MMEs are classified into multiple classes and provide services to UEs subscribing to services of different types, how to select an MME is a problem that urgently needs to be resolved.